1. Technical Field
The present invention relates to a display device that includes a lighting device and a display panel, an electronic apparatus that includes the display device, and the lighting device.
2. Related Art
A liquid crystal device, which is an example of existing display devices, includes a lighting device called a backlight device and a transmissive or semi-transmissive display panel (liquid crystal panel) disposed to overlap a light-emitting surface of the lighting device. The lighting device includes a light guide plate and a plurality of light emitting elements aligned so as to oppose one of the sides of the light guide plate that serves as a light-receiving surface, for example as disclosed in JP-A-2009-3081.
In many of the thus-configured lighting devices, for example as shown in FIGS. 10A and 10B, light emitting elements 89 are mounted on a surface 881 of a light source substrate 88, and the light source substrate 88 is fixed with screws 86 to a light source support member 60 made of a metal. Although the screws 86 are fastened from the side of the light source support member 60 according to JP-A-2009-3081, actually it is often inevitable to fasten the screws 86 from the side of the surface 881 of the light source substrate 88, owing to spatial restriction of the peripheral structure and for the sake of working efficiency.
Another example of the techniques thus far proposed is dividing the plurality of light emitting elements 89 into groups and controlling light intensity with respect to each of the groups, to thereby control the intensity of the illuminating light from the lighting device for each region. Such technique is called local dimming, and provides improved image contrast and moving picture display performance.
However, in the case where the screws 86 are fastened from the side of the surface 881 of the light source substrate 88 as shown in FIGS. 10A and 10E, the position where each screw 86 is located assumes different surface conditions from those of the adjacent regions in the longitudinal direction of the light source substrate 88. This leads to a drawback in that the luminance of the illuminating light becomes uneven, resulting in remarkable degradation of image quality. Especially in the case where the light emitting elements 89 are grouped in a plurality of groups G (group Ga, Gb, Gc, . . . ) in the longitudinal direction of the light source substrate 88 and the light intensity is controlled with respect to each of the groups G, the position in each group G where the screw 86 is located assumes different surface conditions (structural shape, projection and recess, step, surface roughness, color, texture, and so forth) from those of the adjacent regions. Accordingly, diffusion and reflection of the light become discontinuous and/or uneven and hence the light introduced through the light-receiving surface of the light guide plate is unevenly distributed. Consequently, uniform luminance expected from a flat-surface (plate-shaped) lighting device is unable to be achieved, and the image quality is remarkably degraded.
Such a drawback similarly arises even though, for example, a recess 886 is formed at the position where the screw 86 is located so that the screw head is kept from protruding from the surface 881 of the light source substrate 88. In addition, even though a hook is employed in place of the screw 86 so as to retain the light source substrate 88, or a recess is formed on the light source substrate 88 so that a projection formed on the light source support member 60 is fitted therein, the foregoing drawback is unable to be solved, as long as a positioning structure such as the hook or the projection is exposed on the surface 881 of the light source substrate 88.